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Chemistry 2e

# Key Terms

Chemistry 2eKey Terms

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amplitude
extent of the displacement caused by a wave
atomic orbital
mathematical function that describes the behavior of an electron in an atom (also called the wavefunction)
Aufbau principle
procedure in which the electron configuration of the elements is determined by “building” them in order of atomic numbers, adding one proton to the nucleus and one electron to the proper subshell at a time
blackbody
idealized perfect absorber of all incident electromagnetic radiation; such bodies emit electromagnetic radiation in characteristic continuous spectra called blackbody radiation
Bohr’s model of the hydrogen atom
structural model in which an electron moves around the nucleus only in circular orbits, each with a specific allowed radius
continuous spectrum
electromagnetic radiation given off in an unbroken series of wavelengths (e.g., white light from the sun)
core electron
electron in an atom that occupies the orbitals of the inner shells
covalent radius
one-half the distance between the nuclei of two identical atoms when they are joined by a covalent bond
d orbital
region of space with high electron density that is either four lobed or contains a dumbbell and torus shape; describes orbitals with l = 2.
degenerate orbitals
orbitals that have the same energy
effective nuclear charge
charge that leads to the Coulomb force exerted by the nucleus on an electron, calculated as the nuclear charge minus shielding
electromagnetic radiation
energy transmitted by waves that have an electric-field component and a magnetic-field component
electromagnetic spectrum
range of energies that electromagnetic radiation can comprise, including radio, microwaves, infrared, visible, ultraviolet, X-rays, and gamma rays
electron affinity
energy change associated with addition of an electron to a gaseous atom or ion
electron configuration
listing that identifies the electron occupancy of an atom’s shells and subshells
electron density
a measure of the probability of locating an electron in a particular region of space, it is equal to the squared absolute value of the wave function ψ
excited state
state having an energy greater than the ground-state energy
f orbital
multilobed region of space with high electron density, describes orbitals with l = 3
frequency (ν)
number of wave cycles (peaks or troughs) that pass a specified point in space per unit time
ground state
state in which the electrons in an atom, ion, or molecule have the lowest energy possible
Heisenberg uncertainty principle
rule stating that it is impossible to exactly determine both certain conjugate dynamical properties such as the momentum and the position of a particle at the same time. The uncertainty principle is a consequence of quantum particles exhibiting wave–particle duality
hertz (Hz)
the unit of frequency, which is the number of cycles per second, s−1
Hund’s rule
every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin
intensity
property of wave-propagated energy related to the amplitude of the wave, such as brightness of light or loudness of sound
interference pattern
pattern typically consisting of alternating bright and dark fringes; it results from constructive and destructive interference of waves
ionization energy
energy required to remove an electron from a gaseous atom or ion
isoelectronic
group of ions or atoms that have identical electron configurations
line spectrum
electromagnetic radiation emitted at discrete wavelengths by a specific atom (or atoms) in an excited state
magnetic quantum number (ml)
quantum number signifying the orientation of an atomic orbital around the nucleus
node
any point of a standing wave with zero amplitude
orbital diagram
pictorial representation of the electron configuration showing each orbital as a box and each electron as an arrow
p orbital
dumbbell-shaped region of space with high electron density, describes orbitals with l = 1
Pauli exclusion principle
specifies that no two electrons in an atom can have the same value for all four quantum numbers
photon
smallest possible packet of electromagnetic radiation, a particle of light
principal quantum number (n)
quantum number specifying the shell an electron occupies in an atom
quantization
limitation of some property to specific discrete values, not continuous
quantum mechanics
field of study that includes quantization of energy, wave-particle duality, and the Heisenberg uncertainty principle to describe matter
quantum number
number having only specific allowed values and used to characterize the arrangement of electrons in an atom
s orbital
spherical region of space with high electron density, describes orbitals with l = 0
secondary (angular momentum) quantum number (l)
quantum number distinguishing the different shapes of orbitals; it is also a measure of the orbital angular momentum
shell
atomic orbitals with the same principal quantum number, n
spin quantum number (ms)
number specifying the electron spin direction, either $+12+12$ or $−12−12$
standing wave
(also, stationary wave) localized wave phenomenon characterized by discrete wavelengths determined by the boundary conditions used to generate the waves; standing waves are inherently quantized
subshell
atomic orbitals with the same values of n and l
valence electrons
electrons in the high energy outer shell(s) of an atom
valence shell
high energy outer shell(s) of an atom
wave
oscillation of a property over time or space; can transport energy from one point to another
wave-particle duality
observation that elementary particles can exhibit both wave-like and particle-like properties
wavefunction (ψ)
mathematical description of an atomic orbital that describes the shape of the orbital; it can be used to calculate the probability of finding the electron at any given location in the orbital, as well as dynamical variables such as the energy and the angular momentum
wavelength (λ)
distance between two consecutive peaks or troughs in a wave
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